Abstract: Semi-objective analysis method designed by Samel et al, Mann-Kendall test method and moving t-test technique are used based on the understanding of rainy season in order to investigate the beginning and end dates of rainy season over North China.The yearly initial date and final date of rainy season over North China are set up, and their climatological dates are further identified. The results show that rainy season in North China has an average duration of 50 days, starting on Jun 30 and ending on Aug 18 from climatology aspect. The period of heavy rainfall for the rainy season in North China is from Jul 19 to Aug 14, which is also the mature period of summer monsoon.The initial date, end date and the duration of rainy season and the frequency of no rainy season have regional features over North China. Rainy season has the earliest staring dates, late ending dates, longer duration days and the lowest frequency of no rainy season in the mountainous areas on the north of Hebei Province. Late starting dates and higher frequency of none rainy season are in the Loess Plateau while the latest ending dates and the longest duration days are on the north of the Loess Plateau. The earlier starting date, the earliest ending date, the shortest duration days and higher frequency no rainy season are in the mid-lower Basins of Yellow River, and the latest starting date, late ending date, longer duration days and highest frequency of none rainy season are in the west of Hebei plain. There are different trends for the initial dates, end dates, duration days of rainy season and frequency of none rainy season over North China. Duration days of rainy season have the most significant decreasing trend and the end dates also have obvious decreasing trend, while the total stations have significant increasing trend and the initial dates also have a slight increasing trend. All of these trends are of benefit to the decrease of summer rainfall over North China. There are close relationships between the rainfall of rainy season over North China and the initial dates, duration days of rainy season, the total stations of none rainy season. When rainy season begins earlier(later), duration days of rainy season last longer(shorter), the total stations are more(less), rainfalls of rainy season over North China are more(less).When positive anomalies of geo-potential height over the west Pacific exit, meanwhile negative anomalies of geo-potential height in the 500 hPa filed exit over North China, and the pattern is an anomalies of "east high and west low" between the Chinese mainland and west Pacific in the surface, the results are that the anomalies of south wind reach 30°N, the rainy season begins over North China. However, when smaller positive anomalies of geo-potential height in the 500 hPa field exit over North China, positive anomalies of geo-potential height in the 500 hPa field exit over Japanese sea, and the pattern is anomalies of "west high and east low" between the Chinese mainland and west Pacific, the results are that the anomalies of north wind influence Eastern China, the rainy season ends in North China.